Server Client names

Hello,
I’ve been following a web server example, and since I"m trying to learn the language, I’ve been going through it trying to learn each piece. There are a couple things I don’t understand, hoping someone can help me out. Thanks
I will post two pieces of code here, hoping my explanation is clear… In this first piece, the ethernetclient is called “client” so to println to the client, they used client.println(“Then all the stuff to send as HTML…” So far I’m ok with this, See next section, to see my problem

First Piece of Code,

EthernetClient client = server.available();  // try to get client

    if (client) {  // got client?
        boolean currentLineIsBlank = true;
        while (client.connected()) {
            if (client.available()) {   // client data available to read
                char c = client.read(); // read 1 byte (character) from client
                HTTP_req += c;  // save the HTTP request 1 char at a time
                // last line of client request is blank and ends with \n
                // respond to client only after last line received
                if (c == '\n' && currentLineIsBlank) {
                    // send a standard http response header
                    client.println("HTTP/1.1 200 OK");
                    client.println("Content-Type: text/html");
                    client.println("Connection: close");
                    client.println();
                    // send web page
                    client.println("<!DOCTYPE html>");
                    client.println("<html>");
                    client.println("<head>");
                    client.println("<title>Arduino LED Control</title>");
client.println("<form method=\"get\">");
                    ProcessCheckbox(client);

In the below Code, a new function is created which decides what to send as HTML to a client.
Ok, I"m fine with that, BUT what I don’t get is why now, in this function is the client now referred to
as “cl” instead of client as it was in the above section.
Also; 2nd question, the function name says processcheckbox(ethernetclient cl) - and i’m not sure why.
When this function is called above is has “client” in the parenthesis. Again, not sure why.
Thank you

void ProcessCheckbox(EthernetClient cl)
{
    if (HTTP_req.indexOf("LED2=2") > -1) {  // see if checkbox was clicked
        // the checkbox was clicked, toggle the LED
        if (LED_status) {
            LED_status = 0;
        }
        else {
            LED_status = 1;
        }
    }
    
    if (LED_status) {    // switch LED on
        digitalWrite(2, HIGH);
        // checkbox is checked
        cl.println("<input type=\"checkbox\" name=\"LED2\" value=\"2\" \
        onclick=\"submit();\" checked>LED2");

That's the fundamental way functions are defined, declared, and called in the C programming language. See: https://www.arduino.cc/en/Reference/FunctionDeclaration

Thank you. but still unclear as to why in the main code when the function is called, why it has "client" in the parenthesis... what is that telling it to do to the function ? and why in the function is the client referred to as cl ... sorry if Im not clear

Did you look at the examples at the link? They do EXACTLY the same thing.

Yes, thank you I looked over the link you sent. So is having function_name(ethernetClient cl ) the same as having function_name (int x ) in the example in the link you sent? it's just saying a type, and the name ?

If so, why in that function, do you need to refer to the client as cl, when all along outside the funtion the client was referred to as client ? Would I not be able to print to the same client called client, from within the function. or it Needs to be called cl within the function ?

This probably explains it better than I can: https://en.wikipedia.org/wiki/Parameter_(computer_programming)#Parameters_and_arguments

katana_flyer: Yes, thank you I looked over the link you sent. So is having function_name(ethernetClient cl ) the same as having function_name (int x ) in the example in the link you sent? it's just saying a type, and the name ?

If so, why in that function, do you need to refer to the client as cl, when all along outside the funtion the client was referred to as client ? Would I not be able to print to the same client called client, from within the function. or it Needs to be called cl within the function ?

Yes, it is like having a type and the name.

In the ProcessCheckbox function declaration, you have told the program "I'm going to receive an ethernetClient from whatever calls and inside this function I'm going to refer to it as cl."

No matter what the client is called in the main function, in the ProcessCheckbox function, it is called cl.

In the main program, you could have created two clients.

EthernetClient clientA = server.available();
EthernetClient clientA = server.available();

//and each one of them you could have called 

ProcessCheckbox(clientA);
ProcessCheckbox(clientB);

then, when the program jumps into "ProcessCheckbox", it doesn't care what the name of the thing you gave it was. It's just going to call it "cl".

ProcessCheckbox(); looks like a function to me that just wants to read the data from the client.

Did you write the code where it's doing cl.println() or is that part of the code you're getting from elsewhere? If I can make some guesses at what's going on, it doesn't seem like cl should be printing. It should just be "processing the checkbox" and then sending information on that back to the client in the main program.

If you want to actually change the original client, there is a different syntax for passing it into ProcessCheckbox.

ahh, okay, TheCityGame, thank you - that clears alot up for me. I didn't write the code, it was a sample I had taken from an example online, but I was picking it apart to try to learn how and why.

GFvalvo, thank you as well for your replies. I think after going thru your responses I have a better understanding now. If I get stuck I will post again. Thanks alot.